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pytest 核心功能-重新运行失败的测试并在测试运行之间保持状态

2022-03-21 11:28 更新

用法

该插件提供了两个命令行选项来重新运行上次 pytest 调用的失败：

--lf, --last-failed - 只重新运行失败。
--ff, --failed-first - 先运行失败，然后运行其余测试。

对于清理（通常不需要）， --cache-clear 选项允许在测试运行之前删除所有跨会话缓存内容。

其他插件可以访问 config.cache 对象以在 pytest 调用之间设置/获取 json可编码值。

只重新运行失败或先运行失败

首先，我们创建50个测试调用，其中只有2个失败:

# content of test_50.py
import pytest


@pytest.mark.parametrize("i", range(50))
def test_num(i):
    if i in (17, 25):
        pytest.fail("bad luck")

如果你第一次运行这个，你会看到两个失败:

$ pytest -q
.................F.......F........................                   [100%]
================================= FAILURES =================================
_______________________________ test_num[17] _______________________________

i = 17

    @pytest.mark.parametrize("i", range(50))
    def test_num(i):
        if i in (17, 25):
>           pytest.fail("bad luck")
E           Failed: bad luck

test_50.py:7: Failed
_______________________________ test_num[25] _______________________________

i = 25

    @pytest.mark.parametrize("i", range(50))
    def test_num(i):
        if i in (17, 25):
>           pytest.fail("bad luck")
E           Failed: bad luck

test_50.py:7: Failed
========================= short test summary info ==========================
FAILED test_50.py::test_num[17] - Failed: bad luck
FAILED test_50.py::test_num[25] - Failed: bad luck
2 failed, 48 passed in 0.12s

然后如果你用 --lf 运行它：

$ pytest --lf
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-7.x.y, pluggy-1.x.y
rootdir: /home/sweet/project
collected 2 items
run-last-failure: rerun previous 2 failures

test_50.py FF                                                        [100%]

================================= FAILURES =================================
_______________________________ test_num[17] _______________________________

i = 17

    @pytest.mark.parametrize("i", range(50))
    def test_num(i):
        if i in (17, 25):
>           pytest.fail("bad luck")
E           Failed: bad luck

test_50.py:7: Failed
_______________________________ test_num[25] _______________________________

i = 25

    @pytest.mark.parametrize("i", range(50))
    def test_num(i):
        if i in (17, 25):
>           pytest.fail("bad luck")
E           Failed: bad luck

test_50.py:7: Failed
========================= short test summary info ==========================
FAILED test_50.py::test_num[17] - Failed: bad luck
FAILED test_50.py::test_num[25] - Failed: bad luck
============================ 2 failed in 0.12s =============================

您只运行了上次运行的两个失败的测试，而 48 个通过的测试还没有运行。

现在，如果您使用 --ff 选项运行，所有测试都将运行，但之前的第一个失败将首先执行：

$ pytest --ff
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-7.x.y, pluggy-1.x.y
rootdir: /home/sweet/project
collected 50 items
run-last-failure: rerun previous 2 failures first

test_50.py FF................................................        [100%]

================================= FAILURES =================================
_______________________________ test_num[17] _______________________________

i = 17

    @pytest.mark.parametrize("i", range(50))
    def test_num(i):
        if i in (17, 25):
>           pytest.fail("bad luck")
E           Failed: bad luck

test_50.py:7: Failed
_______________________________ test_num[25] _______________________________

i = 25

    @pytest.mark.parametrize("i", range(50))
    def test_num(i):
        if i in (17, 25):
>           pytest.fail("bad luck")
E           Failed: bad luck

test_50.py:7: Failed
========================= short test summary info ==========================
FAILED test_50.py::test_num[17] - Failed: bad luck
FAILED test_50.py::test_num[25] - Failed: bad luck
======================= 2 failed, 48 passed in 0.12s =======================

新的 --nf，--new-first 选项：首先运行新测试，然后是其余测试，在这两种情况下，测试也按文件修改时间排序，最近的文件首先出现。

上次运行中没有测试失败时的行为

如果在上次运行中没有测试失败，或者没有找到缓存的 lastfailed 数据，则可以使用 --last-failed-no-failures 选项将 pytest 配置为运行所有测试或不运行测试，该选项采用以下选项之一：

pytest --last-failed --last-failed-no-failures all    # run all tests (default behavior)
pytest --last-failed --last-failed-no-failures none   # run no tests and exit

新的 config.cache 对象

插件或 conftest.py 支持代码可以使用 pytest 配置对象获取缓存值。这是一个基本示例插件，它实现了一个在 pytest 调用中重用先前创建的状态的fixture：

# content of test_caching.py
import pytest
import time


def expensive_computation():
    print("running expensive computation...")


@pytest.fixture
def mydata(request):
    val = request.config.cache.get("example/value", None)
    if val is None:
        expensive_computation()
        val = 42
        request.config.cache.set("example/value", val)
    return val


def test_function(mydata):
    assert mydata == 23

如果你是第一次运行这个命令，你可以看到 print语句：

$ pytest -q
F                                                                    [100%]
================================= FAILURES =================================
______________________________ test_function _______________________________

mydata = 42

    def test_function(mydata):
>       assert mydata == 23
E       assert 42 == 23

test_caching.py:20: AssertionError
-------------------------- Captured stdout setup ---------------------------
running expensive computation...
========================= short test summary info ==========================
FAILED test_caching.py::test_function - assert 42 == 23
1 failed in 0.12s

如果您再次运行它，将从缓存中检索该值，并且不会打印任何内容：

$ pytest -q
F                                                                    [100%]
================================= FAILURES =================================
______________________________ test_function _______________________________

mydata = 42

    def test_function(mydata):
>       assert mydata == 23
E       assert 42 == 23

test_caching.py:20: AssertionError
========================= short test summary info ==========================
FAILED test_caching.py::test_function - assert 42 == 23
1 failed in 0.12s

检查缓存内容

您始终可以使用 --cache-show 命令行选项查看缓存的内容：

$ pytest --cache-show
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-7.x.y, pluggy-1.x.y
rootdir: /home/sweet/project
cachedir: /home/sweet/project/.pytest_cache
--------------------------- cache values for '*' ---------------------------
cache/lastfailed contains:
  {'test_caching.py::test_function': True}
cache/nodeids contains:
  ['test_caching.py::test_function']
cache/stepwise contains:
  []
example/value contains:
  42

========================== no tests ran in 0.12s ===========================

--cache-show 采用可选参数来指定用于过滤的全局模式：

$ pytest --cache-show example/*
=========================== test session starts ============================
platform linux -- Python 3.x.y, pytest-7.x.y, pluggy-1.x.y
rootdir: /home/sweet/project
cachedir: /home/sweet/project/.pytest_cache
----------------------- cache values for 'example/*' -----------------------
example/value contains:
  42

========================== no tests ran in 0.12s ===========================

清除缓存内容

您可以通过添加 --cache-clear 选项来指示 pytest 清除所有缓存文件和值，如下所示：

pytest --cache-clear

对于来自持续集成服务器的调用，建议这样做，因为隔离和正确性比速度更重要。

Stepwise

作为 --lf -x 的替代方案，特别是对于您预计大部分测试套件将失败的情况，--sw, --stepwise 允许您一次修复一个。测试套件将一直运行到第一次失败，然后停止。在下一次调用时，测试将从上一个失败的测试继续，然后运行直到下一个失败的测试。您可以使用 --stepwise-skip 选项忽略一个失败的测试并在第二个失败的测试上停止测试执行。如果您陷入失败的测试并且只想在以后忽略它，这很有用。提供 --stepwise-skip 也将隐式启用 --stepwise